ALBERT

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Double-wire double-pulsed gas metal arc welding (DP-GMAW) experiments were conducted in the double pulse synchronous (DPS), alternating (DPA), and independent (DPI) phases. The effects of current phase on weld seam formation were analyzed. Experimental results showed that a stable welding process was achieved in all three current phases and the derived weld seams demonstrated little spatter, no hump, or undercut. Different current phases had little influence on weld reinforcement and width, but had a significant influence on weld penetration and toe angle. The fish-scale ripples of weld seams were prominent; specifically, the fish-scale ripples in the DPA phase were more prominent than those in other current phases. The penetration and penetration shape factor (PSF) in the DPA phase were at their highest while those in the DPS phase were at their lowest. In the DPS phase, the ferrite was coarse and in higher quantity, while the pearlite was relatively in lower quantity. In the DPA phase, the ferrite was finer and in lower quantity, while the pearlite was relatively in higher quantity and the microstructure was more uniform. Last, in the DPI phase, the microstructure appeared in a state between the DPS and DPA phases.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Thermal issues become more serious for high-speed and high-precision motorized spindle. Thermal error compensation is cost-effective and convenient to implement for this problem. To further improve the machining accuracy of the motorized spindle with shaft core cooling, this study aims to develop simple thermal error compensation model based on only the rotational speed of spindle and without any temperature data to predict the thermal error. In this study, a special measurement system was established to measure the axial thermal deformation of a motorized spindle with shaft core cooling at various speeds. A thermal error compensation model based on the exponential function was established using the experimental data. This model needs only two parameters—operating rotational speed and duration—of the motorized spindle to predict the thermal deformation and then can be easily and quickly executed without adding any extra hardware. The model is verified by comparing with experimental data at constant speeds of 4200 rpm and 7000 rpm as well as the stepped speed. The results show that the model has higher accuracy and better robustness. Under experimental conditions, when the motorized spindle operates at constant rotational speed, its accuracy increases by about 90% after compensation; when the motorized spindle operates at stepped rotational speed, the maximum thermal deformation of the motorized spindle is 29.95 μm before compensation and 2.01 μm after compensation, the accuracy of which increases by 93.2%.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The aim of this study is to identify the limitations of self-supporting structures and evaluate the deformations associated with overhang structures fabricated without support structures. To achieve these objectives, a series of experiments involving different overhang geometries were designed, fabricated, and evaluated. The formation of defects during the fabrication of overhanging structures is detailed, and the self-supporting limits for different overhangs are established. A segmentation strategy for the support structure addition is proposed and evaluated in different configurations for ledge overhangs to reduce the amount of support structures without affecting the overhang accuracy. Based on the inferences of this study, design rules are proposed for producing overhang structures through electron beam melting. The results identified the self-supporting limits for different overhang geometries. In addition, the proposed segmentation strategy for support generation in ledge overhangs resulted in reduction of support structure materials and post-processing time without any effect on the quality of the fabricated overhang.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉This paper addresses the use of two algorithms based on symbolic dynamics analysis of vibration signal for fault diagnosis in gearboxes. The symbolic dynamics algorithm (SDA) works by subdividing the phase space described by the Poincaré plot into several angular regions; then, a symbol is assigned to each region. The probability distributions generated by the set of symbols are considered as features for classification of faults in a gearbox. The peak symbolic dynamics algorithm (PSDA) is a variant that extracts a sequence of peaks from the vibration signals and then performs the phase-space subdivision and symbol coding. A gearbox vibration signal dataset is analyzed for classifying 10 types of faults. Fault classification is attained using a multi-class support vector machine. The highest accuracy attained using 〈em〉k〈/em〉-fold cross-validation is 100.0% for load L3 with SDA and 100% with load L2 with PSDA. The accuracy considering all signals in the gearbox dataset is 99.2% with SDA and 99.8% with PSDA. The algorithms proposed have the advantage of being simple, accurate, and fast, and they could be adapted for online condition monitoring.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The monitoring of tool condition in machining processes has significant importance to control the quality of machined parts and to reduce equipment downtime. This study investigates the application of a special variant of artificial neural networks (ANNs), in particular, wavelet neural network (WNN) for tool wear monitoring in CNC end milling process of high-speed steel. A mixed level design of experiments with machining parameters of cutting speed, feed rate, cutting depth, and machining time is developed, from which 126 experiments are conducted. For each experiment, tool wear and surface roughness of machined workpiece are measured. The tool wear images are processed, and the descriptor of wear zone is extracted. The WNN is then applied to predict the flank wear of the cutting tool and compared with commonly used types of ANNs and the statistical model. Different input combinations with the inclusion of wear zone descriptor and surface roughness of machined parts are used to evaluate the performance of all models. Results show that the WNN with the input parameters of cutting speed, feed rate, depth of cut, machining time, and descriptor of wear zone predicts the degree of tool wear most accurately.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The centrifugal disc finishing process is an abrasive technique of mass machining, and it is very effective but very frequently time consuming. In this paper, a simulation of the centrifugal disc finishing process was presented in order to estimate the kinetic energy distribution of the working medium and to find its regions that make the process more efficient. Numerical results were obtained using an explicit method in the Ansys/Ls-Dyna program. Due to the fact that the physical properties of numerous objects in free motion need to be calculated in a simulation process, the discrete element method (DEM) was used. Results from the numerical simulations indicate that the velocity and energy of particles is variable in an axial cross-section of working medium. The article presents particle velocity distributions in the working chamber for various rotational speeds of the rotor. The typical changes in velocity in the function of time are also discussed. Statistical important functions of the average kinetic energy of the working medium and accumulated energy by machining surface have been estimated in respect to the rotational speed and machining time with a high value of adjustment coefficients. This article constitutes the first stage of research, which is continued in order to experimentally verify the results in the real process, as presented in the companion paper (Part 2: Experimental analysis with the use of acoustic emission signal).〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Nickel alloys such as Inconel 718 have been widely used in the aerospace, oil and gas, and chemical industries, since they have excellent properties that combine high creep resistance and high mechanical strength, fatigue and corrosion. However, these properties make these alloys extremely difficult to machine, due to a high level of heat generation during material removal, causing rapid wear of cutting tools and a detrimental effect on the surface integrity, reducing the fatigue life of the machined component and lowering the productivity. Looking at the literature, it seemed that there is an opportunity to study the surface integrity of Inconel 718, turned under cryogenic conditions at cutting speeds of 250, 275 and 300 m/min. For these reasons, this work aims to evaluate the influence of the cutting parameters on the surface integrity of Inconel 718 turned under cryogenic conditions using liquid nitrogen (LN2) at high cutting speeds. A whisker-reinforced ceramic tool was used in order to provide wear and shock resistance at high cutting speeds; these are factors that are associated with surface integrity in terms of roughness Ra, residual stresses, microhardness and cutting forces. A central composite design was chosen as factorial planning for the independent variables including cutting speed, feed rate and depth of cut when carrying out the experiments. Cryogenic cooling resulted in an average cutting force of 267 N, where the penetration force was higher. The roughness Ra was 0.52 μm and was influenced by the feed rate and depth of cut. The highest tensile residual stresses in the circumferential direction with LN2 and under dry conditions were 1394 MPa and 1237 MPa, respectively and were influenced by the depth of cut. Small changes in microhardness occurred at a depth of 0.3 mm from beneath machine surface and the presence of a white layer was not observed. Although tensile residual stresses were slightly higher when using LN2 compared to dry machining on the surface, the use of LN2 caused higher compressive residual stresses at the subsurface, which can improve the fatigue life of machined components at high cutting speeds. The results showed that lower cutting parameters tend to give the best results in terms of the cutting force and surface integrity.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The modular design of reconfigurable machine tools (RMTs) is the key enabling technology to reconfigurability. A systematic methodology for setting the constituent modules of RMTs is proposed in this paper. According to the structural and functional characteristics of the components that construct the machine tools, the geometry modules and the basic structure modules are generated, and on this basis, the conceptual autonomous functional modules of RMTs can be constructed. According to the reconfigurable manufacturing process planning for a part family, the optimal processing plans of a family of parts can be obtained, which include a series of processing segments. And through the generated motion-schemes of a RMT of each processing segment, the RMT configurations can be constructed from a set of the autonomous functional modules to meet the process requirements. Finally, a set of RMT modules with particular sizes and structures can be generated, which will be used to construct RMTs to accommodate required changes in existing products or parts. Taking the production of a gearbox part family as an example, the validity of the method is verified.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Robots are widely used in automation because of their flexibility. However, there are still challenges to enhance the effective use of robots in machining process due to unexpected vibration/chatter. Instead of time-consuming trial and error, this paper proposes an expanded mode coupling chatter theory that suits robot kinematics and enables industrial application due to accurate mode coupling chatter prediction. This research allows determination of mode coupling chatter occurrence with respect to constantly changing parameters of robotic kinematic and practical contemplation before setting up the physical robot, workpiece and tool for machining. Firstly, the mathematical model of the robot structure is established and combined with chatter theory. A deepened analysis of stability criteria is carried out followed by experimental validation of the theory. By carrying out this chatter analysis, a software tool based on an algorithm was developed to help determine the stable setup, including machining parameters, robot pose, travel direction and workpiece setup, for a certain robotic machining application. The developed prediction algorithm ties vibration occurrence to machining force direction and magnitude that makes it applicable to various machining operations.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉In virtual cardiovascular surgery and human-robot micro interaction surgery, the force feedback is transmitted via the flexible guide wire. Flexible deformation would make it hard to ensure fidelity only by rendering the force feedback in actuators. This study develops a dynamic model of the guide wire, which is used to simulate the collision of guide wire in the blood vessel or pipeline of the force feedback device. Its dynamic characteristic can be adapted to the design of control strategy of the force feedback and its parameter adjustment. As the force is low, it is easily affected by the motion and friction of the actuator and hand tremor. It puts up the requirement for system robustness. Then, the terminal sliding mode controller is designed to improve the robustness and convergence of the force feedback control. And the research quantitatively evaluates the fidelity of the force feedback control.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The effects of process parameters on microstructure and mechanical properties of the 316L stainless steel helical micro-diameter spring (316L HMDS) fabricated by selective laser melting (SLM) were explored. By optimizing SLM process parameters, the near-full density (〉 99%) SLM-316L HMDS can be manufactured. The SLM-316L HMDS exhibits typical layered morphology consisting of micron-sized melt pools and columnar grains whose growth orientations are consistent with the temperature gradient. Lower hatch space reduces the formation of voids, resulting in better density, elongation, and ultimate tensile strength of the SLM-316L HMDS. The form angle significantly affects the yield strength and ultimate tensile strength, and obvious dimples appear on the fracture surface, demonstrating toughness fracture. The experimental results establish the correlation between the process parameters of SLM and the microstructure and macro-mechanical properties of the SLM-316L HMDS.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉In this study, the effect of particle size and particle content of silicon carbide fillers in epoxy matrix on the mechanical properties and microstructure of the developed composites was investigated. Silicon carbide fillers sized to 〈 45 μm and 90–45 μm were incorporated to epoxy composites to obtain volume fractions of 2, 4, 6 and 8 wt% of SiC. Mechanical properties including flexural strength, compressive strength and hardness tests of the composite samples were performed according to ASTM D790-03 (2003), ASTM D695-15 (2015) and EN 1534 standards. Surface morphology, crack propagation and particulate dispersion were observed using scanning electron microscopes (SEM). The results of the mechanical properties obtained were examined statistically and the results that a strong negative correlation between hardness and flexural strength but the individual correlation between hardness and flexural modulus, compressive stress and compressive modulus were positive. Results also showed that the inclusion of small particulate silicon carbide (〈 45 μm) displayed superior mechanical properties in term of flexural, compressive and hardness characterizations at a given volume fraction. Flexural properties of the composite samples decrease with increase in filler concentrations while the compressive strength and hardness increase as particulate loading increase. In terms of microstructure, uniform dispersion of silicon carbide particulates was observed within epoxy matrix with linear crack propagation.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Motion trajectory commands are usually generated using CAD/CAM software and a specified motion controller. At the CAD/CAM stage, the motion commands are generated with respect to the constrains on the contouring error and the application. These commands are also related to the motion controller, which incorporates an advanced blending interpolation method in its function core. Although, high-speed motion can be achieved using blending interpolation, the accuracy of the trajectory is decreased. This study proposes a new blending method that uses a predefined absolute accuracy to optimize both the speed and the accuracy of the generated motion trajectory. The proposed method uses two strategies: the first accelerates or decelerates the velocity profile and the second inserts an arc trajectory command and the corresponding blending accuracy in a critical segment, in order to achieve the speed and the contouring error that is predefined by the user. Four cases are used to determine the performance of the proposed method: (a) line-to-line, (b) line-to-arc, (c) arc-to-arc, and (d) arc-to-line interpolations. The experiments use a predefined speed and accuracy for the motion trajectory. The results demonstrate that the proposed motion trajectory planning process satisfies the needs of industrial applications such as laser cutting and dispensing.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The influence of the welding and tool rotation speed on morphology and mechanical behavior of friction spot stir welds made on polycarbonate is investigated. The welds were performed in butt configuration. The mechanical behavior of the welds was assessed by means of tensile tests. Digital image correlation (DIC) analysis was performed to determine the strain distribution (over the cross section) during the tests. This enabled to determine the precise position of crack onset and simplified the determination of the welds’ failure. These data were crossed with observation of the welds morphology to better understand the mutual relation among process conditions-morphology and mechanical behavior. The results indicated that the welds produced under low welding speed were characterized by adhesive failure between the stirred region and the substrate. The welds produced under higher speed were affected by excessive thinning. This led to failure in the stirred region or in some cases within the base material due to localized thinning. The mechanical characteristics of the welds were highly correlated to the temperature of the stirred region. This suggests the possibility to use IR thermography for online control and qualitative assessment of the mechanical behavior of the FSW welds made on amorphous thermoplastics.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉This study investigated an influence of the temperature field on thickness distribution of thermoformed products using complex and high-aspect-ratio mold. The optimum temperature field was obtained to achieve a more uniform thickness distribution in the thermoformed products by using finite element simulation. The material properties of acrylonitrile-butadiene-styrene (ABS) polymer sheet were obtained by two rheological measurement tests. The linear viscoelastic properties, such as the storage modulus and loss modulus, were measured by a small amplitude oscillatory shear (SAOS) test for wide ranges of frequency and temperature. The discrete relaxation time and discrete relaxation modulus were obtained by nonlinear regression. The fitting parameters 〈em〉C〈/em〉〈sub〉1〈/sub〉 and 〈em〉C〈/em〉〈sub〉2〈/sub〉 for the WLF model were obtained by curve fitting. The nonlinear viscoelastic property, such as stress relaxation modulus, was measured by a step strain test. The damping function and fitting parameter 〈em〉α〈/em〉 of Wagner-Demarmels (WD) model were determined by curve fitting. Then, the Kaye–Bernstein-Kearsley-Zapas (K-BKZ) constitutive equation was utilized to the thermoforming simulation in order to investigate the material behavior of the polymer sheet. The numerical results showed that a more uniform thickness distribution could be achieved with the optimum temperature field of the sheet. The thinnest part of the products was improved by more than 30%.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉A simulated annealing algorithm combined with an adaptive large neighborhood search (ALNS) has been proposed in this paper to minimize the laser cutting path in a two-dimensional cutting process. The proposed algorithm was capable of finding a near-optimum cutting path from a given layout of cut profiles. In this study, the layout was taken from an image, in which image processing algorithms were employed to extract cut profiles from the input image and to assign coordinates to the contours’ pixels. The optimization algorithm was based on generalized traveling salesman problem (GTSP), where all pixels of the input image were considered as the potential piercing locations. A laser beam made a single visit and then did a complete cut of each profile consecutively. The simulation results revealed that the proposed algorithm can successfully solve several datasets from GTSP-Lib database with a good solution quality. A compromise between the path distance and computing time was achievable by considering only 30% of the total pixels of the input image examined in this study. In addition, the cutting path generated by the proposed method was shorter than that recommended by the commercial CAM software and other previous works in terms of path distance with the same profile sample.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The novel generation of production facilities fostered by the fourth industrial revolution widely adopts different technologies to digitalise the manufacturing and assembly processes. In this context, work measurement techniques are one of the main candidates for the application of these new technologies because of the time, cost, and competences required to analyse manual production activities and considering the limited precision of the traditional approaches. This paper proposes a new hardware/software architecture devoted to the motion and time analysis of the activities performed by human operators within whatsoever industrial workplace. This architecture, called Human Factor Analyser (HFA), is constituted by a network of ad hoc depth cameras able to track the worker movements during the task execution without any interference with the monitored process. The data provided by these cameras are then elaborated in a post-process phase by the HFA to automatically and quantitatively measure the work content of the considered activities through an accurate motion and time analysis. The developed architecture evaluates the worker in a 3D environment considering his interaction with the industrial workplace through the definition of appropriate control volumes within the layout. To test the accuracy of HFA, an extensive experimental campaign is performed at the Bologna University Laboratory for Industrial Production adopting several realistic industrial configurations (different workplaces, operators and tasks). Finally, the HFA is applied to a real manufacturing case study of an Italian company producing refrigerator metal grates. A wide and deep analysis of the obtained key results is presented and discussed.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉In the orbital mode of electrical discharge machining (EDM), an electrode with a complex profile causes deviation in the cavity profile from the design objective. In this paper, electrode compensation techniques according to the envelope theory are presented to eliminate deviation errors. The succession of orbits traced out a family of electrode curves based on kinematic geometry integrated with the motion path of tool bodies and constraints. The boundary of the family of electrode curves is referred to as the orbiting profile. The deviation error between the orbiting and objective profiles can be eliminated by using a compensation electrode in the orbiting process. Thus, the generated orbiting profile conforms to the objective profile. Experimental results of the tested example for the machining profile of the compensation electrode by using the orbital process revealed that profile deviation can be eliminated to ensure that the EDM profile closely conforms to the objective profile. This compensation method for orbiting EDM provided an exact process to engineers for easy control of the machining precision of EDM.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The main objective of this work is to evaluate the tool life and the workpiece surface roughness when applying a vegetable-based cutting fluid by minimum quantity of lubricant (MQL) at three different directions (main tool flank face, secondary tool flank face, and overhead) in turning AISI D6 hardened steel with polycrystalline cubic boron nitride (PCBN) tools with Al〈sub〉2〈/sub〉O〈sub〉3〈/sub〉 ceramic binder and TiN coating. Dry cutting was also tested for comparisons. Tool wear analyses were performed on the tools at the end of their lives within a scanning electron microscope (SEM). The application of the cutting fluid by MQL technique in the direction between the main tool flank face and the workpiece showed better results than the dry condition. The application of MQL through other directions (overhead and between the secondary tool flank face and the workpiece) also showed competitive results. Abrasion and adhesion were the prevailing mechanisms for the wear of the tools.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Cutting tools may heat up during use, causing them to deform. Such an effect degrades the surface microstructure of potassium dihydrogen phosphate (KDP) crystals via ultra-precision fly cutting. In this process, thermal expansion of the tool displaces the tool tip perpendicular to the workpiece processing surface. Such displacement is difficult to measure experimentally due to the limited sensitivity of displacement sensors and the severe conditions present during cutting processes. In this study, a cutting surface simulation model based on machine kinematics of the fly cutting and a thermal model based on the experimental results of the principal cutting forces are established in KDP crystal ultra-precision flying cutting to explore the specific impact on the workpiece due to the thermal deformation of the tool. The relationships between cutting parameters and principal cutting forces are thereby determined. The relationships between tip heat inflow, tip displacement perpendicular to the workpiece processing surface, and crystal surface microstructure were simulated. The results demonstrate that the heat deformation of the tool slightly influences the roughness and waviness of KDP crystal surfaces, and increases their surface slope, thus influencing surface precision. This directly affects the optical performance of such crystals.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Micro dry wire electrical discharge machining (μDWEDM) is a process where gas is used as the dielectric fluid instead of a liquid. In this process, certain modifications of wire electrical discharge machining (WEDM) are needed during the machining operation to achieve stable machining. Smooth and stable machining operation in μDWEDM process remains as a critical issue. Thus, this paper presents the investigation of process parameters for a stable μDWEDM process. The investigation was performed on a stainless steel (SS304) with a tungsten wire as the electrode using integrated multi-process machine tool, DT 110 (Mikrotools Inc., Singapore). The experimentation method used in this phase was a conventional experimental method, one-factor-at-a-time (OFAT). Types of dielectric fluid, dielectric fluid pressure, polarity, threshold, wire tension, wire feed rate, wire speed, gap voltage, and capacitance were the controlled parameters. The machined microchannels were observed using scanning electron microscope (SEM). Stable and smooth machining operation of μDWEDM was found to be with compressed air as the dielectric fluid, workpiece positive polarity, 24% threshold, 0.0809 N wire tension, 0.2 μm/s wire feed rate, and 0.6 rpm wire speed.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Five-axis machine tool is widely used in freeform surface machining. The freeform surface’s tool path is usually discretized as G01 segments and the freeform surface machined with linear interpolation in five-axis machine. Due to the two additional rotary axes, there are the nonlinear coupling relationship between the workpiece coordinate system (WCS) and machine coordinate system (MCS). Hence, there are many uncertain errors produced by the nonlinear coupling relationship, especially via linear interpolation. In order to represent the motion trajectory accurately and generate G01 tool path appropriately, this paper proposes an irredundant G01 tool path generation method for five-axis machine. Firstly, a new tool tip error (TTE) definition is given to reflect the influence of the rotation axis on the tool tip. And then, a new tool orientation error (TOE) definition is given to mirror the tool orientation error caused by rotary axis’ linear interpolation. Finally, an adaptive iterative method (AIM) is proposed to obtain irredundant G01 tool path. By using this method, the G01 tool path can be generated based on the given error limits and the proposed method is verified both in the simulation and experiment. The results show that the proposed method can significantly reduce the number of G01 segments and limit the actual error.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉This paper reported the facile fabrication of high-vanadium high-speed steel (HVHSS) by the conventional powder metallurgy process for the wear-resistant applications. The effect of compaction pressure and of subsequent sintering temperatures on the formability and structural evolution of HVHSS was assessed by scanning electron microscopy (SEM) with electron-dispersive spectra (EDS), and X-ray diffraction (XRD) analysis. The results well revealed the primary constitution composed of mixed hardening phases MC and M〈sub〉6〈/sub〉C existing within the α-ferrite matrix after hot solidification, and the association of microstructural alteration with the sintering temperatures was discussed for as-obtained HVHSS specimens. The HVHSS attained the desirable values of mechanical hardness and bending strength and thereby delivered the capability of friction reduction and wear inhibition, closely depending on the sintering temperature. The optimal sintering condition was determined on the basis of bulk density, shrinkage, and capability assessments. A well-established fabricating route for producing high-quality HVHSS was explored through the combined process of cold compaction and subsequent sintering on the conceptual design of chemical composition and alloying design of commercial M2 steel.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The keyhole behaviors were observed directly by laser welding experiment with quartz glass. Based on Fresnel absorption of laser beam and multi-reflection combined with volume of fluid (VOF) method, a three-dimensional mathematical model was established to study the role of welding speed on keyhole behaviors and keyhole-induced porosity formation in laser welding of aluminum alloy. The keyhole behaviors and weld pool fluid flow were discussed, and the result shows that, although the welding speed varies, the mechanism of keyhole collapse was similar. However, the keyhole stability at higher welding speed was improved due to reduced weld depth fluctuations, spatter number, keyhole depth to width ratio, and keyhole collapse frequency. Furthermore, the improved keyhole stability impeded the keyhole collapse, and the lower weld depth and solidification rate facilitated bubble escaping from the weld pool easily, which are the main factors for suppression of porosity at higher welding speed.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Ultrasonic welding (UW) process offers the ability to create highly efficient solid-state joints for lightweight metal alloys with low power consumption. During the process, a distinct diffusion layer is observed at the joint interface that undergoes severe plastic deformation at elevated temperature. A hierarchical multiscale method is proposed in this study to predict the diffusion behavior of the UW process of dissimilar materials. The method combines molecular dynamics and classical diffusion theory to calculate the thickness of the diffusion layer at the welded interface. A molecular dynamics model is developed for the first time that considers the effect of transverse ultrasonic vibration to simulate the evolution of the diffusion layer. The effect of ultrasonic vibration at the atomic level is assumed to provide thermal energy at the joint interface and the mechanical movement of atoms. The influence of sinusoidal velocity change during ultrasonic vibration is incorporated by numerically time integrating the diffusivity at different ultrasonic velocity. The simulation result shows that the solid-state diffusivity depends on temperature, pressure, and transverse ultrasonic velocity. Higher temperature, pressure, and ultrasonic velocity result in higher diffusivity leading to larger diffusion layer thickness. This article provides a comprehensive review of the diffusion bonding behavior and its dependence on process variables. It also presents a numerical approach combining molecular dynamics and hierarchical multiscale calculation to predict the diffusion layer thickness for the UW process of dissimilar materials.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Tube hydroforming (THF) is a unique forming technique, which can transform metal tubes into complex hollow parts using hydraulic fluid as the forming medium. The initial non-uniform thickness of as-received practical tubes significantly affects their formability in the hydroforming process. A forming limit diagram (FLD), also called as the forming limit curve (FLC), is often adopted to evaluate the forming behaviour of sheet metals in plastic forming processes to avoid forming failures. The purposes of this research are fivefold, namely to establish the FLCs of tubular blanks with varied initial thickness deviations in tensile and compressive strain states by means of finite element (FE) modelling of THF, to construct a non-uniform geometric model for practical tubes, to analyse the impact of initial thickness deviation on the FLCs, to clarify the differences in the FLCs obtained using three different instability criteria, and to validate the proposed non-uniform geometric model by conducting hydro-bulging experiments. Results show that it is possible to accurately predict the FLCs of practical tubes with initial non-uniform thicknesses using FE simulation combined with the proposed non-uniform geometric model. We found that the displacement of FLCs occurred in the major- and minor-strain coordinates because the thickness is initially not uniform; however, no significant discrepancies were observed in the FLCs obtained using the three instability criteria. The proposed approach, which combines FE simulation with a non-uniform geometric model, can be easily employed to predict the ultimate strains of tubes with initial non-uniform thicknesses in THF to avoid forming defects.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The ‘pre-design + optimization’ is one of the main methods to obtain appropriate cooling pipe parameters in hot stamping tools for satisfied quenching quality of hot stamping parts. Since good ‘pre-design’ can effectively reduce the workload of optimization, a novel pre-design method of cooling pipe parameters was put forward and applied in this paper. Firstly, the concept of pipe parameter window and its related building method were proposed, by which the domain of satisfied cooling pipe parameters, under certain quenching process and quality demand, could be obtained. Secondly, the pipe parameter window of drilled cooling pipes, suitable for flat die surface, was built based on the above method, and then used to pre-design the cooling pipes in flat die for application. Finally, the satisfied cooling performance of pre-designed cooling pipes demonstrated the validity of proposed method in guiding the pre-designing of cooling pipe parameters in hot stamping tools.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Transient thermo-mechanical analysis of welding problem requires tremendous computation cost. To accelerate the thermal analysis of large-scale welded structures, an efficient computation scheme based on heat transfer localization and dual meshes was proposed. The computation accuracy is guaranteed by a local fine mesh model with size determined by a theoretical solution and a global coarse mesh model with equivalent heat input. The validity and accuracy of the dual-mesh method were verified using an experimental bead-on-plate model. By extending the weld length, the computation time of the proposed method was proved to be almost linearly dependent on the model scale. The thermal analysis of fillet welding of a large panel structure with 6-m-long weld was accelerated by 10 times over conventional finite element analysis and 2.2 times over adaptive mesh method. Meanwhile, the physical memory consumption was also greatly reduced by the dual-mesh method. Such efficient computation method enables fast evaluation of welding stress and distortion which are vital for manufacturing process and structure performance.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉A type of simulation model for a hot stamping forming process was developed for TA32 high-temperature titanium alloy to study the fracture of a complex aircraft skin by using the forming limit stress diagram (FLSD) as a tool to evaluate the formability. After derivation, the theoretical FLSD of TA32 in the hot forming process is strain rate-dependent and temperature-dependent, which is understood from the constitutive relationship of an Arrhenius-type model. Different stress states were used in this study to evaluate the quality of forming via FLSDs. The results show that the materials develop a resistance to fractures in response to an increase in temperature and a decrease in the formation speed. The predicted results also show that the shape of the blank is an important factor that affects part forming. Tests were performed on the TA32 high-temperature titanium alloy to investigate the effects of the processing parameters and the blank shapes. Several indicators were used to assess forming with respect to the thickness distributions in the safe and dangerous areas by comparing the results of the simulations and experiments. Finally, tensile tests under different states were used to indicate that the experimental and simulation results meet practical engineering requirements.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Through fabricating the micro-textures to improve surface property, the surface texturing technology has become a widely used way to prepare the functionalized surface. This study proposed a surface texturing method of one-dimensional ultrasonic vibration–assisted turning to generate micro-textured end face. The generation principle for the micro-textured end face was presented through the description of cutting conditions, the theoretical analysis of textured features, and the simulation prediction of surface topography. The polycrystalline diamond cutting tools with different clearance angles (7° and 20°) and nose radiuses (400 μm, 200 μm, and 100 μm) were used in the experimental tests to investigate the influence of tool geometry on the micro-dimple features. The results show that the micro-dimples with different sizes and shapes can be successfully fabricated on the end face of Copper 1100. Same as the theoretical analysis and simulation prediction, through changing the cross-sectional profile of dimple along cutting direction, the clearance angle and the radius of observed point were verified to play a key role in the shape of micro-dimple. The oval-like dimples and the scale-like dimples can be respectively manufactured under the different intersection states between the flank face and the cutting trace. It was also confirmed that by choosing proper nose radius and the corresponding feed rate, the textured surface covered by micro-dimples of different widths can be generated. This texturing method used for fabricating the micro-textured end face was verified to be feasible and efficient, which laid a foundation for further research on the application of the textured surface.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉A considerable interest has been generated in recent years in the use of thermoplastic polymers as matrices in the manufacture of advanced composites that require high reliability during long-term operations. In this research, a new Elium® acrylic matrix developed by Arkema was studied to evaluate the accelerated test methodology based on time-temperature superposition principle of Carbon Fiber/Elium® 150 composites. The results show that the high frequencies increase the glass transition (Tg) to higher values because the free volume is favored by polymer chains movement. In addition, artificial neural network has been used to model the temperature-frequency dependence of dynamic mechanical over the wide range of temperatures and frequencies due to its complex non-linear behavior. It has been observed that low frequencies result in low damping due to the lower internal friction, while high frequencies provide greater stiffness to the chains, resulting in a high damping. The long-term life prediction using master curves confirms that this new material can be considered to acoustic or vibrational damping purposes, considering its use in temperatures above Tg.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Product miniaturisation is one of the key aspects of modern manufacturing technology. One of the ways to fabricate miniaturised product is micromachining using sophisticated computer numerically controlled (CNC) machine tools. However, conventional CNC machines are bulky, stationary, and unable to carry out parallel operations. This research aims to develop a modular robotic platform which would be able to carry out machining operation in mesoscale. Hexapod robots are legged mobile robots which are used for verities of applications. Here, we have implemented a hexapod robotic platform to support and move the cutting tool (in this case, a drilling tool). The robot was controlled from the host computer through serial communication. A graphical user interface (GUI) was designed and implemented to operate the robot and the drilling spindle. Several machining operations were carried out with the system to assess its performance. An innovative compensation algorithm has been proposed to improve the positional accuracy of the robot movement. The proposed algorithm takes into account spindle speed and linear velocity to mitigate the positional error. The positional accuracy was improved by more than 60% after implementing the error compensation scheme. In this research we managed to achieve sub-10 μm repeatability (≤ 10 μm) at the lowest spindle and point to point linear speed of 2500 RPM and 200 mm/min, respectively. The performance (in terms of positional accuracy) of the robot was also compared with that of an existing commercial micromachining system where the robot was found to be almost ~ 2× time poorer to that of the commercial machine. Finally, the machined holes’ quality was measured in terms of circularity and taperness. It was observed that at the best machining parameters circularity deviation was as low as 29.4 μm while taperness was 0.54 degree.〈/p〉

Beschreibung: 〈p〉The name of one author was omitted in the initially published version.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Micro components have been demanded increasingly due to the global trend of miniaturization of products and devices. Micro milling is one of the most promising processes for micro-scale production and differs from conventional milling due to the size effect introducing phenomena like the minimum chip thickness, making the prediction of micro milling process hard. Among challenges in micro milling, tool life and tool wear can be highlighted. Understanding tool wear and modelling in micro milling is challenging and essential to maintaining the quality and geometric tolerances of workpieces. This work investigates how to model the diameter reduction of a tool caused by tool wear for micro milling of H13 tool steel. Machining experiments were carried out in order to obtain cutting parameters affecting tool wear by considering the diameter reduction. Dry full slot milling with TiAlN (titanium aluminium nitride)-coated micro tools of diameter 〈em〉d〈/em〉 = 400 μm was performed. Three levels of feed per tooth (〈em〉f〈/em〉〈sub〉z〈/sub〉 = 2 μm, 4 μm and 5 μm) and two spindle speed levels (〈em〉n〈/em〉 = 30,000 rpm and 46,000 rpm) were used and evaluated over a cutting length of 〈em〉l〈/em〉〈sub〉c〈/sub〉 = 1182 mm. The results show that lower levels of feed per tooth and spindle speed lead to higher tool wear with a total diameter reduction over 22%. The magnitude of the cutting parameters affecting tool wear was determined by ANOVA (analysis of variance), and the model validation meets the statistical requirements with a coefficient of determination 〈em〉R〈/em〉〈sup〉2〈/sup〉 = 83.5% showing the feasibility of the approach to predict tool wear using diameter reduction modelling in micro milling.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉In this paper, a new additive manufacturing (AM) process based on extrusion and solid-state bonding is presented. The process uses metal feedstock wire which is processed in a continuous rotary extruder in order to disperse the surface oxides of the feedstock and to provide the required bonding pressure. Simultaneously, the die outlet is scraping the contact surface to provide an oxide-free interface between the extrudate and the substrate. Optical analyses of samples from a layered structure produced from AA6082 reveal that the stringers are fully merged; however, some voids and cracks are observed between the individual stringers. Still, this initial demonstration indicates that the process, upon further development, has high potential of producing near-net-shape parts at high deposition rates.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Laser cleaning has been widely used in manufacturing industries due to its lower pollution and higher cleaning precision and efficiency compared with traditional ways. However, laser cleaning would inevitably induce processing roughness on the workpiece surface and only a few researches have been conducted to this field. In this work, the influence of process parameters on surface roughness was explored in detail. The results showed that process parameters changed surface roughness by changing energy density and overlap ratio. And surface roughness was showed linear positive correlation with energy density. At same energy density, surface roughness will first increase and then decrease with increasing overlap ratios. The maximum roughness was in the range of 50 to 66.7%. It could be explained that after laser irradiation, the sample surface absorbed pulse energy and formed craters. The rim and craters made the sample surface coarse. Due to the depth and diameter of craters were dependent on energy density, the roughness increased with increasing energy densities. The adjacent craters will also change the height of rim and depth of crater with different overlap ratios. It led to different surface roughness.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Additive manufacture (AM) enables the fabrication of highly efficient lattice structures. However, the mathematical efficiency of characterising AM lattice geometry can be poor, potentially restricting the commercial application of AM lattice structures. This research quantifies the effect of the polygon order used to characterise the geometric resolution of lattice strut elements on the associated manufacturability and geometric qualities of the manufactured lattice. The effect of these design parameters on manufactured quality is experimentally determined for aluminium and titanium specimens fabricated by selective laser melting (SLM), although the method can be generally applied to any AM technology. This research finds that geometric thresholds exist, below which additional geometric resolution does not result in increased part quality. These thresholds are a function of material, lattice inclination angle, cross-sectional area and the polynomial order used to represent the cross section. These findings enable significantly reduced computational cost in managing AM lattice structures, and can be directly integrated with algorithmic methods for the optimisation of AM lattice structures.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉A new energy-efficient welding method, flux bands constricting arc (FBCA) welding, is proposed to solve the fabrication of metal sandwich panels. This method is suitable for welding T-joints in special structures where the welding gun is unable to reach the welding position, such as welding thick face-plate metal sandwich panels. The characteristics of FBCA welding, key welding technologies, and corresponding defects and resolutions are discussed. Pull-out tests between T-joints welded by laser and FBCA welding were conducted. Results indicate that complete penetration and good fusion of three-sided T-joint can be produced by FBCA welding. The typical cross section morphology is unlike other common welding methods. T-joints without defects, such as weld asymmetry, root leakage, slag inclusion, and pores, show better ultimate tensile strength than T-joints welded by laser welding. The FBCA welding method can compensate for shortage of insufficient weld width of laser welding.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉This paper is about adding magnetic and ethanol to explore the accuracy of electrochemical discharge machining processing quartz glass. The tool electrode is tungsten carbide rod, the auxiliary electrode is platinum, the power source uses square wave pulse voltage, the KOH electrolyte is added with ethanol, and the tool is added with 3 T magnetic force. The experimental results show that ethanol can stabilize the square wave power supply wave shape, which can reduce the contact angle between the electrode and the bubble. The low contact angle electrolyte can increase the wettability of the tool electrode and improve the electrochemical processing stability. Therefore, under the action of ethanol and a magnetic field, the processing result can be improved, so that the generated bubbles are reduced and the film gets thinned. When the voltage frequency is higher, the film formation thickness will decrease, and the magnetic force and voltage will induce the magnetohydrodynamics of the electrolyte, which will make the electrolyte and bubble flow around the electrode relatively stable, the circumference around the aperture is flat, and the roundness is obviously improved. The overall improvement in the taper of the machined hole is increased by about 30%, and the amount of undercut of the hole is reduced.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Due to the complicated deformation of the billet in roll forming process and the lack of the theoretical understanding, there are still no unified methods to design and optimize roll profiles. Theoretical analysis of the deformation in roll forming process based on mathematical method is efficient and necessary. A qualified roll profile optimization method should be based on the accurate calculation of the spatial configuration of the billet. However, the existing models for calculating the spatial configuration of the billet in roll forming process cannot calculate the springback of the billet. In this paper, according to the mathematical model established by the author for calculating the spatial configuration of the billet, a roll profile optimization method for high-strength V channel roll forming process was proposed by taking the maximum edge membrane longitudinal strain as constraint conditions. After optimization, the number of roll stands required for final V channels was reduced from 8 to 5. Through analyzing and comparing the deformation of the billet in simulation results of bending and roll forming process, it is found that bending tests can also be used to verify the feasibility of the roll profile optimization method proposed in this paper. The bending tests were carried out using the original and optimized process parameters, respectively. The results show that the shape of the V channel obtained by the optimized process parameters is much closer to that of the designed V channel.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉A process variant of electromagnetic sheet forming, known as radial Lorentz force augmented deep drawing, has been recently developed to promote the material flow control in high-velocity forming process. Unlike conventional electromagnetic sheet forming, this new process introduces an additional radial inward Lorentz force at the flange region to enhance the draw-in material flow. Previous works have illustrated the feasibility of the process for altering the dynamic deformation behavior and, therefore, the final deformation morphology. This paper further explores the versatility of this process on deformation control by scheduling a wider range of the discharge voltage combinations. While previous works reported two potential types of the final deformation profiles, i.e., convex and flat shapes, this paper further suggests a concave shape and shows adjustment of the deformation profile in a flexible manner by altering the process parameters. To reveal the control rule for forming shape, we established two process windows in terms of two discharge voltages or in terms of draw-in and forming height, based on experimental and numerical results. In addition, new insights into the mechanisms behind different deformation modes have been gained from the analysis of the dynamic deformation process. This work demonstrates the versatility of the process, which offers an improved ability for deformation control in the context of electromagnetic sheet forming.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Residual stress in additive manufacturing (AM) is one of the key challenges in terms of structural integrity and the finish quality of printed components. Estimating the distribution of residual stresses in additively manufactured components is complex and computationally expensive with full-scale thermo-mechanical FE analysis. In this study, a point heat source is utilized to predict the thermal field and residual stress distribution during the manufacturing processes. Numerical results show that the residual stress at a single material point can be expressed as a function of its spatial position and the peak nodal temperature it has experienced during thermal cycles. The distribution of residual stress can be divided into three segments according to the peak nodal temperature. The peak nodal temperature only depends on the heat flux and the distance to the point heat source center. A semi-analytical approach to predict the peak nodal temperature and residual stresses, once the heat flux is known, is proposed. The proposed approach is further validated by a numerical case study, and a very good agreement has been achieved. Compared with traditional thermo-mechanical FE analysis of additive manufacturing, the proposed method significantly improves the computational efficiency, showing great potential for prediction of residual stresses and distortion.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Abrasive fluidized bed (AFB) machining of aluminum samples was studied with a specific focus on surface roughness formation, according to the sample position inside AFB operating in a minimum fluidization regime. The experimentation was aimed at defining optimum process conditions in terms of morphology uniformity and developing a mathematical model which relates the sample position to the final roughness. Measurements performed by profilometry have shown that a uniform average roughness lower than 1 μm can be obtained, starting from 3.5 μm, when the process parameters and handling are optimized. The analysis of variance (ANOVA) was performed to support the experimental and modeling strategy. This study led to the definition of a rapid and efficient procedure for finding the optimal positioning of samples in terms of finishing and surface uniformity. The proposed procedure does not require complex systems for component movement, and it is based on the study of just two reference positions of samples. The advantage of the procedure developed and validated in this study consists in its ease of implementation and its applicability in industrial strategies, where short decision times are essential.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Milling freeform surfaces using a STEP-compliant CNC machine tool highly reflect the intelligence of STEP-NC, especially when the toolpaths can be generated and adjusted online. However, in contrast to the 2.5D manufacturing features, there are very seldom entities defined in the standard ISO 14649-11 for milling freeform surfaces. Basically, there are only four freeform strategies used for finish milling a freeform surface, and no roughing operations are provided for milling a freeform surface from a raw piece to the shape before the (semi-)finishing operation. Obviously, both of the rough and finish operations are fundamental to machine a freeform surface from the raw piece. This paper extends the EXPRESS definitions for rough milling freeform surfaces, so as to enrich the related operations. Both 2.5D and freeform operations are improved, and individual operations, strategies, and technologies are added to fulfill the need of 2.5D and freeform roughing tasks respectively. The related online toolpath generation algorithms are developed and integrated into a STEP-CNC prototype. The STEP-CNC system is equipped to a three-axis machine tool and finally drives the machine tool to cut a T-spline surface.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Amid diversification, high performance, high integration, and low-cost development in consumer electronic products, the conventional system on board function integration model is giving way to system on chip (SoC). Layout of solder balls under ball grid array (BGA) is getting irregular as system in package (SiP) is integrating multi-chip module and couple of active and passive components along with more complex circuit design. Due to the shortening life cycles of consumer electronic products and frequent new product launches, the incoming inspection operation of electronic components is getting tedious, let alone the component database updates required by mounter are also getting more frequent and time consuming due to increasingly complex and diversified components and soaring demands in characteristic measurement and identification difficulties. This study is aimed at building automated characteristic capture and analysis image processing model for BGA packages of irregular solder ball layout. It employs edge detection to get component body looks and dimensions by enhanced component edge characteristics. A image pre-processing model is used to identify consistency of individual solder ball characteristics with median filter, highlight image characteristics with binary conversion, remove noise with morphology, and connected component labeling to segment area covered by individual characteristic. In addition, a roundness and aspect ratio of the least rectangle-based solder ball characteristics identification method is proposed to determine number of, diameter of, and coordinates of center of border solder balls. The component characteristics acquired by the model comes in ± 3% difference against the actual one in terms of dimension. The model appears a good reference for system packaging operator in component database creation for the launch of new products in terms of reduced time for manual measurement and error as well as loss in mounter capacity. It also serves for electronic components incoming inspection to reduce inspection operation time and simplify the process.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Global interference detection and avoidance are key issues in tool path planning for five-axis machining of complex surfaces. Improving the detection accuracy and efficiency has always been the main goal of global interference research. In this paper, a novel method for fast interference judgment is proposed. First, the four planes with X or Y extremum are obtained by the intersection operation between the plane and the machined surface and solving extremum, respectively. Then, the four boundaries of the initial interference detection area are obtained by intersecting the four extreme planes with the machined surface. To determine whether there is collision interference between the tool and the machined part, the shortest distance between the tool axis and the detection area is used for interference judgment. The shortest distance can be obtained by calculating the distance between the discrete point in the detection area and the tool axis. In order to ensure the uniformity of the discrete points, the discretization of points was carried out in the projection area of the initial detection area on the XOY plane, rather than on the part surface. For improving the efficiency of interference detection, the four-sided constraint method is used to screen the discrete points in the initial detection area. Only the points satisfying the screening conditions can be used as effective detection points to calculate the distances, and the shortest distance can be found from all the calculated distances. In this paper, the subdivision technology is used to achieve high-precision interference detection. At the end of the paper, the interference detection algorithm was tested by two examples, and the correctness of the test results was verified by the VERICUT simulation and cutting experiment. The proposed algorithm can be applied to interference detection of five-axis end milling of complex surfaces.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Conventional volumetric error compensation strategies for five-axis machines directly generate compensation values without considering the RTCP (rotation tool center point) effects, which causes additional movements of translational axes with the movement of rotary axes, so the compensation values for three linear axes need to be recalculated. In this paper, a volumetric error compensation model considering RTCP is proposed. In the model, the compensation values for translational axes totally consist of three parts, i.e., position errors caused by the volumetric error, position variations caused by the compensation of rotary axes, and caused by RTCP. Firstly, the compensation values for rotary axes are obtained based on the volumetric error model and the inverse kinematics. Then, the compensation values for three linear axes are calculated in detail based on the compensation values of rotary axes and RTCP effects. Finally, ballbar tests of a cone-frustum toolpath are selected to verify the proposed compensation model.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The remanufacturing technology of aero-engine blade is one of the effective ways to save expensive materials such as titanium alloy, make full use of resources, and solve the problem of resource hiding. Laser-cladding technology has been widely used in the remanufacturing of blades due to its ability to fabricate high-performance alloy surfaces on metal substrates without affecting the properties of the matrix. In order to solve the problem that the grinding precision is difficult to guarantee due to the deformation and residual distribution of the blade in laser cladding remanufacturing, the self-adaptive grinding process of abrasive belt is repaired based on online inspection and reconstruction model. Firstly, the distribution of theoretical measuring points is planned based on the curvature of cross-section curve, and then the theoretical measurement points are adaptively extracted according to the improved firefly algorithm, so that the CMM measurement path planning of laser cladding and remanufacturing blades is realized. Taking the layer as the unit, the measurement data are processed, and the iterative nearest point algorithm is used for data registration to realize the laser-cladding remanufacturing blade measurement data processing. On this basis, the blade surface model is obtained based on NURBS interpolation. Finally, a laser cladding and remanufacturing blade of an aero-engine was tested. The experimental results show that the blade surface roughness is 0.4 μm, the blade edge accuracy is less than 0.05 mm, and the blade edge error is less than 10%. The experimental results show that this method can effectively solve the grinding process of laser-cladding remanufacturing blade.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Recently, in the automobile industry, the use of zinc-plated high-strength steels has been increasing to lighten vehicles and improve safety. In this scenario, gas metal arc welding (GMAW) processes are applied to automobile bodies and chassis parts. However, porosity defects occur in the welds because of the zinc vapor formed in the zinc coating layer during the GMAW process. This causes a decrease in the strength of the welded portion. These porosity defects have internal porosity and external pits, but in the actual production line, the quality of the welds is assessed by the occurrence of defects in external pits. In this study, using arc voltage and a system based on the waveform of the welding current, feature variables were extracted to characterize the sizes of external pits formed in high tensile strength galvanized steel during the GMAW process. Subsequently, a size prediction model was applied to predict the sizes of the external defects in the pits, and the results were verified using a multiple linear regression model and an artificial neural network.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉In the present study, tailor-welded blanks (TWBs) of dissimilar material combination were fabricated by laser welding of interstitial-free (IF) and dual-phase (DP) steels using 2.4-kW power and 4 m/min scan speed. Subsequently, TWBs of as-received sheet materials and IF steels were pre-strained up to 20% major strain in the deformed specimens through an equi-biaxial pre-straining setup. It was found that highly non-uniform strain distribution with nearly plane strain deformation mode was induced in the pre-strained TWBs, whereas an equi-biaxial strain was recorded for IF monolithic blank. Microhardness profiles and the effect of weld zone on the microstructural and mechanical properties of the as-received and pre-strained TWBs were studied. Further, the forming limit diagrams (〈em〉ε〈/em〉-FLDs) of as-received TWB and IF steel were experimentally evaluated. The 〈em〉ε〈/em〉-FLD of pre-strained TWBs was experimentally determined, and 〈em〉ε〈/em〉-FLD of the pre-strained IF material was estimated using the Yld89 anisotropy plasticity model with the Hollomon hardening law. Subsequently, all these respective 〈em〉ε〈/em〉-FLDs were implemented as damage models in the FE simulations for predicting the limiting dome height (LDH) of as-received and pre-strained TWBs. It was observed that the error in LDH prediction of pre-strained TWB domes was within 9.1% when the estimated 〈em〉ε〈/em〉-FLD of the pre-strained IF material was used as a damage model. The FE-predicted strain distributions and weld line movements of TWBs after the second stage of deformation were also successfully validated with the experimental data.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉In this paper, the effect of clamping time on welding distortion is studied. The welding process has been done in austenitic stainless steel 304L butt-welded joint by TIG welding method. The numerical thermo-mechanical analysis is performed using commercial finite element software ABAQUS. The welding simulation is performed using the birth and death of elements technique. The heat source model that used in this study is the Goldak double-ellipsoidal model. At last, for verifying numerical results, a set of experimental tests have been carried out and welding distortion has been measured. The experimental measured data are compared with numerical (FEM) results. The results showed that the clamping causes change in direction of bending and angular distortions (opposite of without clamping mode). Any increase in clamping time relatively causes a decrease in angular and bending distortions. A 70% reduction of angular and bending distortions were observed in cold release mode (unclamping after the workpiece has cooled down to room temperature) compared with hot release mode (an immediate unclamping after welding). The position of clamping has a significant effect on distortion reduction as well. If clamping position is moved closer to the weld line, the distortion is decreased. By reducing relative clamping distance of 60 to 20 mm, the angular distortion is reduced to 0.15 mm which is about 25% and bending distortion of 0.6 mm (40%) can be achieved. The angular and bending distortions are increased when the sheet width is reduced during the experiments. It should be noted that the measured results of experiments and numerical method are in a relatively good agreement and the amount of error is within the acceptable limits.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉This paper is concerned with a method for quality control– and evaluation-based measurements and advanced methods of modeling and identification systems. The variability of properties is measured by the magnitude of the distance between the output of the model and the required measurement; the variability level depends on the several factors affecting the distribution of the measurements during different manufacturing and operational steps. The objective of this work is to evaluate the variability of the properties of material using inferential model and measurements; it usually used multivariate regression. The main local chemical elements of material at a specified point obtained by a scanning electron microscope (SEM) are analyzed using a hybrid scheme based on the identified measurement models and Monte Carlo simulation. The variability assessment is quantified by modeling errors obtained by the propagation of random input changes through the model. A comparative study between different techniques based on intelligent methods is given; the variability is monitored, and control limits are defined using statistical tools. This kind of approach is applied for constructing an accurate computing procedure for variability analysis and quality assurance.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Tool wear is an important consideration for Computerized Numerical Control (CNC) machine tools as it directly affects machining precision. To realize the online recognition of tool wear degree, this research develops a tool wear monitoring system using an indirect measurement method which selects signal characteristics that are strongly correlated with tool wear to recognize tool wear status. The system combines support vector machine (SVM) and genetic algorithm (GA) to establish a nonlinear mapping relationship between a sample of cutting force sensor signal and tool wear level. The cutting force signal is extracted using time domain statistics, frequency domain analysis, and wavelet packet decomposition. GA is employed to select the sensitive features which have a high correlation with tool wear states. SVM is also applied to obtain the state recognition results of tool wear. The gray wolf optimization (GWO) algorithm is used to optimize the SVM parameters and to improve prediction accuracy and reduce internal parameters’ adjustment time. A milling experiment on AISI 1045 steel showed that when comparing with SVM optimized by commonly used optimization algorithms (grid search, particle swarm optimization, and GA), the proposed tool wear monitoring system can accurately reflect the degree of tool wear and achieves strong generalizability. A set of vibration signals are adopted to verify the presented research. Results show that the proposed tool wear monitoring system is robust.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉SCA (softness consolidation abrasive) finishing is a new type of machining method. The dilatancy effect of abrasive particles during processing causes the local accumulation of abrasives particles and leads to scratches on the surface of the workpiece, which in the meantime decreases finishing efficiency. So, microscopic contact mechanic model of abrasive particles is established to analyze the force chain transfer phenomenon. A microscope constitutive model of abrasive particles is established to reflect the microscopic force-displacement relationship between abrasive particles. The force chains net evolution of the abrasive particles with different porosity and the surface stress distribution of workpieces are simulated by PFC3D.The results show that when the porosity exceeds 44%, the internal force chain transmission path of the abrasive particles disappears; the surface stress of workpieces exhibits a periodic distribution. As the porosity increases, the stress amplitude decreases. Finally, the test platform is set up and the laws of porosity and abrasive’s size on surface roughness of workpieces can be concluded after a series of polishing experiments by pneumatic wheels with softness consolidation abrasive. The experiments results show that when the abrasive’s size is 800 and the porosity is 24%, the surface roughness of workpieces is small, and the surface average roughness of workpieces can decrease from 313.744 to 67.11 nm.〈/p〉

Beschreibung: 〈p〉The article Prediction of surface roughness in milling process using vibration signal analysis and artificial neural network, written by T. Y. Wu and K. W. Lei, was originally published electronically on the publisher’s internet portal (currently SpringerLink) on 03 January 2019 without open access.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Although there are methods to machine free-form surfaces, serious distortion in the concave–convex characteristic of the flattened-plane boundary, high deformation of the surface geometry, and single limitation of the surface topology are usually produced. Thus, a novel surface flattening method is proposed in this paper to retain the concave–convex characteristic and reduce the deformation, and a spiral path is generated to machine the free-form surface with various topologies. The machined surface is mapped to a planar region with a free boundary using a fusing constraint mapping method. First, the spring-mass-based stretching constraint is used to minimize the length differences of the triangular sides, which are caused by surface flattening. Subsequently, in order to flatten surfaces with an isometric deformation, we perform this operation under the constraint of hinge-based bending. Eventually, the global constraint, the minimization of the global energy, is employed to acquire a less distorted plane. Then, to generate a planar spiral path fit for machining various planes, which are concave, convex, simply-connected, or multiply connected, enrichment of the conventional Voronoi diagram, interpolation between the wave fronts, and rounding of the spiral polyline are implemented. For machining a free-form surface, by inversely mapping the planar path, a spiral tool path is planned. Experimental results are given to illustrate the effectiveness of the presented methods.〈/p〉

Beschreibung: 〈p〉The following row in Table 5 under the category “Stochastic mathematical programming” is missing.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Geometric accuracy is a critical performance factor for machining, especially when one of the basic requirements is high precision. In this paper, a general and systematic approach is shown to model hole geometric deviation from nominal due to the geometric errors of three important elements of the drilling process: the locators, the workpiece datum surface and the machine tool. The proposed approach was used for calculating the deviation from nominal of lots of drilled holes on a plate in order to evaluate the influence of the locator errors, of the form deviation of the part datum surfaces and of the volumetric error of the machine tool. Those parameters’ influence was evaluated through a design of experiments technique with a factorial plane implemented in a Matlab® file, allowing a saving of time, energy and material. It was found that the volumetric error of the machine tool influenced mainly the drilled hole location deviation from nominal.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉As a nontraditional type of processing technology, ultrasonic-assisted grinding (UAG) can effectively improve the surface integrity. A considerable research effort has been devoted to investigate the impact of various processing parameters on surface roughness. However, few studies have been conducted on the effects of matching relationship between different parameters. In this study, the numerical model of a dressed grinding wheel is constructed using a measured diamond pen. Based on the grinding kinematics, the micro surface topography of the workpiece is generated. The relationship between surface roughness and three main processing parameters is studied, and the concept of critical ultrasonic amplitude is proposed. It is found that the ultrasonic grinding can effectively weaken the deterioration of the roughness by increasing the depth of cut, and then, the relationship between the critical ultrasonic amplitude and the depth of cut is obtained. Furthermore, the coupling relation is explained from the angle of a single abrasive grain. Finally, the accuracy of the findings is verified by the experimental results, which may serve as an effective method or reference for the setting of ultrasonic grinding parameters.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉A new theoretical model was presented based on the conversion of ultrasonic vibration to heat. The provided model was used as the definition of material behavior in the finite element simulation. According to this model, the temperature of the tools increased rapidly in the early stages of vibration and then reached to a constant value. The experimental results showed the reduction of the amount of force and coefficient of friction under the influence of vibration. In this regard, good congruence was obtained between the results of the numerical solution and the experimental results. To further understanding the effect of ultrasonic vibrations on material properties, the microstructures of deformed specimens were examined. Microscopic observation of specimens under the influence of vibration showed equiaxed fine grains along the primary grain boundaries which their partial volume in the structure was increased by increasing the vertical step down and horizontal feed rate.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The current study aims to investigate the effects of process parameters on mechanical and microstructural characteristics of Al 6061-SiC composite fabricated via squeeze casting. Seventeen experiments in total have been conducted according to Box-Behnken experimental design which contained three process parameters (squeeze pressure, melt temperature, and SiC wt.%) while recording the responses including ultimate tensile strength, hardness, and percentage elongation. ANOVA (analysis of variance) was employed to evaluate the significance and prediction capability of mathematical models developed through regression analysis. The results indicate that squeeze pressure, melt temperature, and SiC wt.% significantly affect the responses whereas ductility is drastically reduced at higher concentrations of SiC reinforcement. SEM micrographs of failed test specimen have been found to be indicative of ductile fracture at higher levels of squeeze pressure and melt temperature. The multi-objective optimization problem has been transformed to an equivalent single-objective problem using grey relation analysis. The desirability analysis revealed optimum setting of process parameters which was confirmed to have improved the ultimate tensile strength by 1.61%, hardness by 1.56%, and percentage elongation by 11.11% as compared to the initial setting.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Many studies have used different optimisation methods to find a near-optimal solution by optimising the disassembly operations sequence. These studies have used disassembly operation time as the main optimisation parameter, and other parameters such as direction change or tool change are converted to time scale. In order to determine accurate operation time, a product needs to be completely disassembled, noting that the same EOL products can be in a different condition and result in different operation time. In this work, new optimisation parameters based on the disassemblability and components demand are defined. These include Disassembly Handling Index (DHI), Disassembly Operation Index (DOI) and Disassembly Demand Index (DDI). In order to consider the operation time and other costs, Disassembly Cost Index (DCI) is further defined. Genetic algorithm optimisation method was employed to optimise the process sequence. Here, the most demanded components with the easiest disassembly operations are disassembled first without requiring to disassemble the unwanted components and avoid complicated operations. Two case studies were analysed to determine the effectiveness and compatibility of this method. The result shows 13% and 10% improvement in overall disassembly time for the case studies.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Modern day technology demands consistent and frequent advancements in materials for specialized applications. Nickel aluminide is one of such materials with distinctive properties that make them particularly suitable for high temperature applications especially in aerospace industries. However, the lack of ambient temperature ductility of this intermetallic has greatly restricted its applicability in service. In this review, the various efforts of researchers in solving this major limitation of nickel aluminides is evaluated and summarized, with particular emphasis on reinforcement types and processing methods that have been explored over the years.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Water absorption restrains the mechanical performance of natural fibre reinforced matrix polymer. This paper aims to investigate the influence of water absorption on the different types of natural woven fibre reinforced with polyester resin. The water absorption and thickness swelling study were performed by an immersed composite sample in the distilled water for 30 days. The mechanical performance testing such as tensile testing, flexural and impact was performed on the single and hybrid composite. Based on the results obtained, water absorption of the single type and hybrid composite sample yield about 3–6%. Furthermore, the effect of thickness of swelling is at a minimum. The result of the tensile properties reveals that the layering size has more influence than the layering sequences. The flexural properties are likely to be affected by the type of fabric fabricated on the top. The results of the Charpy impact test show that there is possibly less variation for the value regardless of the layering sequence and the layering size. The water absorption drops the tensile strength about 12–27% and tensile modulus for 15–35% on the 30th day. The result shows that the resistance toward water absorption improved significantly toward hybridisation.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Nickel alloys have the ability to resist extreme conditions; as a result, they are in evidence among different industrial areas. Nickel alloy machining is often associated with high manufacturing costs and low productivity. Cutting-edge tool geometry is one of the key factors in order to enable high-performance cutting operations with these alloys. Besides that, the cutting fluid use can reduce friction and temperature. On the other hand, dry machining brings environmental benefits and, in addition, it can protect the factory worker from several diseases caused by the contact with the cutting fluid. Therefore, experimental tests were realized, focusing on understanding the surface integrity behavior after milling of Inconel 718. The experiments occurred with the use of original and polished tools. Besides that, the milling process was performed in dry and MQL conditions. The texture, roughness, hardness, and affected layer were tightly studied. A great difference was found in texture and roughness behavior among dry-machined surfaces and with MQL application, due to thermal and friction effects. Cutting-edge preparation showed better results in this case, as original tool edges were sharp. The smaller affected layer deformations were obtained by original tools with MQL application, and hardness measurements did not exhibit significant variation. Among the tested conditions, the best performance was achieved with the use of MQL and, in general, cutting-edge preparation did not show significant variation.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The emergence of Cyber Physical System has dramatically impacted the use of traditionally centralized control system in responding to unexpected events. Rush order is a quite common unexpected event in the current dynamic market characteristics and has significant perturbing ability to a centrally predictive schedule. This paper is aimed to propose a consensus algorithm for multi-agent-based manufacturing system (CoMM) to control the rush order and henceforth minimize a makespan. Consensus is an algorithmic procedure applied in control theory which allows convergence of state between locally autonomous agents collaborating for their common goal. Leader-follower communication approach was used among the multi-agent to deal with the perturbing event. Each agent decides when to broadcast its state to neighbor agents, and the controlling decision depends on the behavior of this state. The consensus algorithm is initially modeled by networking all contributing agents. After this, it is validated with simulation experiment based on academic full-sized ap plication platform called TRACILOGIS platform. The results showed that the consensus algorithm has significantly minimized the impact of rush order on makespan of manufacturing orders launched on a system.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉This paper proposes a cascading fuzzy logic algorithm with image processing technique for defect detection and classification on the lateral surface of industrial cylindrical object using a camera and multiple flat mirrors. The finishing surface of industrial parts such as shafts, bearings, pistons, rings, and pins should be smooth within permissible limits before installation process, as the defects in these parts may damage or reduce the life of the whole machine. The optical surface inspection of cylindrical products and highly curved surfaces is quite challenging in the industrial automation, due to that it needs to be acquired with several views and subsequently combined in one view. Thus, a time–cost-effective visual inspection method with fuzzy logic–based decision making approach is developed to investigate the optical defects on the lateral surfaces of the cylindrical products. The image processing algorithm has been developed to extract the main features of the tested objects such as defects, borders, and noise. A cascading fuzzy logic algorithm with two stages has been implemented to eliminate the effect of the noise in the captured images and thereafter classify the objects into defective and non-defective objects. The 1st stage of fuzzy logic algorithm is used to eliminate the low noise from the captured images; however, the 2nd stage is used to differentiate between the big noise and defects on the objects. Results show that the defects can be detected if the ratio of detection is higher than 0.1 and the accuracy of defectiveness levels is 80%.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The paper studies the post-grinding temperature distribution on the inner ring of ball bearing 7008C. A grinding model was proposed to calculate the temperature distribution using the finite element method. The grinding process was simplified based on abrasive grain grinding motion. Our calculation takes account of the non-linear variation in physical properties of the bearing material as the temperature changes and the effects of convective heat transfer in the surrounding environment. A rectangular heat source and cyclic loading method were used to simulate the energy input during grinding, and the grinding temperature fields under different processing parameters were obtained. The calculated temperature fields are in good agreement with experimental results. The proposed model was then utilized to analyze the influence of different processing parameters on the temperature distribution, providing a basis for predicting the phase change and analyzing the post-grinding residual stress. Through processing parameter adjustments, the optimal parameter combinations that do not lead to material phase changes were identified. We hope this analysis will shed some light on the optimization of the bearing grinding process.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The molten pool temperature during laser engineered net shaping (LENS) could directly affect the microstructure and phase compositions of materials in the molten pool, thereby affecting the mechanical properties of the fabricated parts. To achieve a well-built solid structure, the research on fundamentals and methods of molten pool thermal behavior monitoring is of great significance. Using a high-resolution infrared camera, this paper realized real-time temperature tracking of Inconel 718 deposition in the LENS process. The effects of deposition variables, such as laser power and scanning speed, on the molten pool temperature and cooling rate have been investigated. In addition, the effects of the molten pool temperature on the molten pool depth and dendrite arm spacing (DAS) have been analyzed. The results suggest that the molten pool temperature increases with increasing of the laser power while it drops first and then rises with increasing of the scanning speed. The molten pool temperature increases nonlinearly with increasing of the number of layers during the material deposition process.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The nuclear reactor coolant pump (NRCP) is the heart of the nuclear power plant. This paper focuses on robot automation grinding processing for NRCP, which includes scanning, point cloud processing, grinding trajectory generation, and quality evaluation system based on reverse engineering. In this work, firstly, the point cloud of NRCP is obtained by robotic scanner system of hand-eye calibration. Secondly, the research proposes a novel method for point cloud simplification, denoising, and boundary extraction base on 〈em〉k〈/em〉 neighborhood octree structure. More important, the efficient trajectory generation of grinding relies on transforming point cloud into adaptive triangular mesh. Lastly, quality evaluation system can calculate the deviation between point cloud and qualified workpiece. And the further path is generated according to the deviation. Experiments show that the accuracy of “246” hand-eye calibration method is less than 0.02 mm. The method of point cloud processing has obvious efficiency advantages over other researchers’ algorithms. The final results indicate that the error of grinding is less than 3 mm and efficiency can be improved by 2.5 times compared with manual grinding.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The structure and mechanical properties of carbonized coconut shell nanoparticles (CSnp) reinforced epoxy composite have been evaluated to establish the possibility of using the composite as a new material for automobile car bumper application. Epoxy resin of the type LY556 was blended together with CSnp at 5–25 wt%. Scanning electron microscopy (SEM), mechanical test, and thermogravimetric analysis (TGA) were examined. SEM morphology reveals adhesion between CSnp and polymer matrix at low wt%CSnp while at higher weight percent of CSnp agglomeration of CSnp was observed. The addition of CSnp at 25 wt% produced the optimal hardness values of 26.35 VHN, tensile stress of 338.75 MPa, and flexural strength of 156 MPa, while at 10 wt% CSnp produced optimal impact energy value of 5.71 J. The developed epoxy composite when compared with two existing Toyota models showed improved impact energy at break of 10.5% over Big Daddy Model and 37.45% over Carina model under the same testing conditions.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉This is the first literature survey of its kind on aggregate production planning (APP) under uncertainty. Different types of uncertainty, such as stochasticity, fuzziness and possibilistic forms, have been incorporated into many management science techniques to study APP decision problem under uncertainty. In current research, a wide range of the literature which employ management science methodologies to deal with APP in presence of uncertainty is surveyed by classifying them into five main categories: stochastic mathematical programming, fuzzy mathematical programming, simulation, metaheuristics and evidential reasoning. First, the preliminary analysis of the literature is presented by classifying the literature according to the abovementioned methodologies, discussing about advantages and disadvantages of these methodologies when applied to APP under uncertainty and concisely reviewing the more recent literature. Then, APP literature under uncertainty is analysed from management science and operations management perspectives. Possible future research paths are also discussed on the basis of identified research trends and research gaps.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉This paper investigates the influence of cutting conditions on the formation mechanism of chips using a tungsten carbide in-house lasered cutter (grooved chip breaker) and a benchmark commercial cutter during turning of AISI1040 medium carbon steel. Microstructure of the free surface and segment underside the chips are experimentally characterised via scanning electron microscopy (SEM) and white light interferometry. The mechanism of chip formation is classified into continuous, partially segmented, segmented and discontinuous. Chip breaking ability is achieved for all tested feed speeds at depth of cut above 1.2 mm, marking the transition from continuous to segmented chips. The chip breaker manufactured via a nanosecond laser proves to enable for the first time breaking of the chip below a feed rate of 0.1 mm/rev outperforming the commercial cutter and showing viability for the production capabilities of lasers for mass manufacture. Lamellae-type chips are revealed from machining using the lasered tool, while brush-stroke chips are discovered and introduced for the first time from machining using the benchmark cutter. While the lamellae form from cleavage cracks due to strain incompatibility at inclusions caused by an excess in critical shear strain. The brush-stroke chips are caused by a localised increase of temperature at the tool/material interface which lead to thermal softening of the workpiece: the resulting surface experiences large areas of plastic deformation. For the in-house lasered tool, at higher cutting speed, the shear strain hardening reduces the flow stress of the workpiece material in the shear zone.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉During the fabrication of composite parts, the residual stresses build up causing the shape distortion in laminated composites and deteriorate its mechanical performance. In the case of angled/cylindrical parts, the stress leads to the change in the encircled angle. The effect of adding nano/microparticles on the mechanical properties has been the focus of many researchers in the recent past, but their effect on the process induced shape distortion of composite parts has been studied rarely. This study investigates the effect of silica particles on shape distortion in glass/unsaturated polyester cross-ply C-shaped composite parts having an enclosed angle of 240°. Composite parts were fabricated with a varying fraction of silica particles (0, 3, 5, and 7% by weight of resin). In order to analyze curing behavior, thermal kinetics of the resin system was investigated using differential scanning calorimetry (DSC). The experimental results showed that the value of diameter reduction was reduced from 6 mm to 3 mm by addition of 5% silica particles. Furthermore, composite part distortion was predicted using an analytical model and compared with experimental results for validation.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉A still current challenge of paramount importance for manufacturing metrology is the industry and laboratories’ increasing demand for faster inspection and verification measuring procedures to determine the conformance of products to dimensional or functional requirements. Within this context, a measuring system group that has gained great importance in the field of high precision dimensional verification are the portable coordinate measuring machines (PCMMs) such as articulated arm coordinate measuring machine (AACMM). Nevertheless, an important drawback of these type of instruments are the time-consuming, tedious, and expensive tasks inherent to their verification and kinematic parameter identification procedures. In this work, a kinematic parameter identification procedure of an AACMM by means of an indexed metrology platform is presented. Moreover, the kinematic modeling of the AACMM is developed, and the optimization of the arm kinematic parameters to minimize the measurement error is carried out in terms of eight objective functions. Finally, a comparison between the optimized parameters and the nominal parameters is discussed, showing the advantages of using the indexed metrology platform (IMP) in the optimization procedure.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉This paper proposes an approach for twist springback reduction using variable blank holder force (VBHF) trajectory that the blank holder force (BHF) varies through the stroke. In addition, the blank shape is optimized. Therefore, design optimization of VBHF trajectory and blank shape for twist springback reduction is performed. Springback of U-shaped product is a simple deformation, whereas the one of S-rail-shaped product shows more complicated behavior due to twisting. As the result, compared with the springback of U-shaped product, it is difficult to evaluate the twist springback. A novel evaluation method for the twist springback is proposed, and the optimal VBHF trajectory and blank shape for the twist springback reduction are determined under several design constraints. Numerical simulation of the S-rail-shaped product is so intensive that response surface approach is valid. In particular, a sequential approximate optimization that the response surface is repeatedly constructed and optimized is used to determine the optimal VBHF and blank shape. Through numerical result, the validation of the proposed approach is examined.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉An innovative cold spray method for the deposition of ferromagnetic particles is presented. A magnetic field is used to magnetize and then accelerate the sprayed particles towards the substrate. In addition, the magnetic attraction focuses the trajectories of the particles so that their spreading is reduced. This magnetic assisted cold spray achieves higher deposition efficiencies in comparison with the conventional process. The quality of the produced coatings, as regard their porosity, is increased too. The proposed method shows promises of being a useful tool to expand the industrial applications of cold spray.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Titanium and its alloys are associated with low density and excellent strength/weight ratio, biocompatibility in surgical implants, high mechanical strength at high temperatures and excellent corrosion resistance. The Ti6Al4V alloy is applied in the aerospace, biomedical, chemical, naval and petrochemical industries. However, these alloys present problems during machining and are therefore considered materials of difficult machinability at high cutting speeds. This paper aims to analyse the wear mechanisms in cutting tools using cemented carbide (H13A) and synthetic polycrystalline diamond (PCD) in the high-speed turning of Ti6Al4V alloy, under the following cooling conditions: dry, jet and minimum quantity lubricant (MQL). To measure wear, a microscope was used to measure flank wear in the tools. Next, the images of these tools were obtained using scanning electron microscopy for the identification of the wear mechanisms. According to the results, the variation in the cutting parameters (cutting speed and feed rate), type of tool material, as well as the cooling conditions significantly affects the behaviour of the wear mechanisms. The wear mechanisms presented in the cutting tools are not the result of one single mechanism, but a combination of many mechanisms. Overall, the primary type of wear is flank wear and the mechanisms are abrasion, adhesion and attrition (adherence and drag).〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉This paper deals for the first time with the effects of additional cooling medium by submerging underwater on the feasibility of dissimilar bond formation between aluminum and steel in solid-state during friction-stir welding (FSW) process. Sheets of AA5083 Al-Mg aluminum alloy and A441 AISI steel are considered into the investigation with a butt-joint design and immersing under the cooling water mediums with three different temperatures of 0, 25, and 50 °C besides ambient processing in the air atmosphere without excessive cooling. Thermo-mechanical cycles during the FSW process are monitored as well as the soundness of produced dissimilar weldments in terms of materials inter-mixing, grain structural features, possible phase transformations, mechanical property, and subsequent fracture behavior. The results showed that by increasing the cooling capability of the environment and employing the low-temperature water as the submerged medium, the peak temperature during the FSW process is continuously reduced down to ~ 400 °C. The impact influence is on suppressing the dissimilar metals inter-mixing as well as the grain structural coarsening during dynamic recrystallization and the kinetics of intermetallic compound (IMC) formation. By decreasing the peak temperature and submerging under cooling medium, the thickness of the IMC layer at the interface is continuously decreased as affected the indentation hardness resistance and subsequent transverse tensile behavior. All samples are failed at the joint interface along the IMC layer, with an excellent combination of tensile strength (~ 310 MPa) and elongation (~ 13%) for the room temperature cooling medium, as the optimum condition based on the evolution of experimental trends. The dominant flow mechanism as plastic constraint induced some fractural aspects of ductile in dimpler form or catastrophic on the corresponding failed portion depending on the joint brittleness.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉For the purpose of processing some forms of diamond, such as polycrystalline diamond (PCD) and chemical vapor deposition diamond, picosecond pulsed laser (PSPL) has the decisive advantage of wear-free material removal. This availability of picosecond pulsed laser sources enables the efficient applications of cutting diamond to generate sharp and regular cutting edge. Therefore, in this study, picosecond pulsed laser is used to fabricate polycrystalline diamond (PCD) micro tool. In order to optimize the picosecond pulsed laser processing, the effects of PSPL cutting parameters including the pulse energy, pulse pitch, and grain size of PCD on the cutting results are investigated. The results indicate the grain size has the greatest impact on the cutting edge radius and pulse energy has great effect on the processed surface of PCD. The results prove that PSPL is a better choice for precision fabrication of PCD micro tool. Finally, the fabrication of PCD micro tools by PSPL has been demonstrated.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The mechanism of serrated-chip formation is a basic theoretical foundation for metal cutting. Much research has concentrated on the shear formation characteristics of serrated-chip formation. However, compression deformation has not been proposed to elucidate serrated-chip deformation within the primary zone. This paper proposes a computational model considering compression deformation in the primary zone. Compression deformation characteristics are obtained by combining the model with the results of a high-speed orthogonal cutting experiment. In a high-speed orthogonal cutting experiment on Ti-6Al-4V at cutting speeds of 10–160 m/min and feed rates of 0.07–0.11 mm/r, the compression stress (1134–1600 MPa) decreased with the cutting speed and feed rate. The compression strain (0.10–0.22) and strain rate (0.09 × 10〈sup〉4〈/sup〉/s–0.75 × 10〈sup〉4〈/sup〉/s) increased with the cutting speed and decreased with the feed rate. The temperature of the primary zone (272.3–417.2 °C) increased with the cutting speed and feed rate.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Competitive companies which are guided by the productivity enhancement employ the lean tools such as single-minute exchange of die (SMED) to reduce the setup time. This study presents a review of the state-of-the-art literature including 130 articles related to single-minute exchange of die and proposes a classification and analysis of the reviewed works. The classification was based on categories, areas, research methods, tools, implementation, results, and countries. This review emphasizes lean tools within the single-minute exchange of die technique. To this end, the study allows dissemination of the knowledge gained from the literature on single-minute exchange of die, and it presents the classified articles that used the Shingo stages in the implementation of the setup reduction.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉While it is well recognized in the literature that modularity is a very important enabler for reconfigurability in manufacturing systems, there is very limited practical guidance on how the various required functions of a production system should be grouped into modules. In this work, a new heuristic approach is developed and presented, to aid the system developer in the identification and synthesis of potential modules during the early design stage of a reconfigurable manufacturing system. The work involves the identification of key module drivers for such systems, and of key criteria that can be used to facilitate the optimization of the granularity and effectiveness of the system. The results are presented in the form of a semi-algorithmic design tool that can be easily understood and used by the developer. The tool is applied to three very different industrial case studies, and is shown to be applicable to various manufacturing scenarios and sub-sectors. The use of the new tool is compared to the use of a design structure matrix approach to function clustering for module synthesis, and is shown to be easier and more objective in its application.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Extreme tool wear resulting in short tool life is one of the main issues in the cutting process of near-beta Ti alloys. This study provides extensive experimental results and new findings that help to understanding progressive tool wear and the corresponding measures in high speed machining of Ti-5553 alloy under various coolant and lubrication (dry, flood, high-pressure coolant, MQL, and Cryogenic cooling) conditions at finish and semi-finish cutting. Cutting temperature, progressions of tool wear, and tool life are presented. Besides, cutting forces, frictional conditions, and chip morphology are studied. This current work provides evidence that supports the argument that the feasibility of high speed machining of near-beta titanium alloys that depends on cutting conditions, namely coolant and lubrication used during machining. It was found that tool wear is developed by an abrasive and adhesive mechanism, and built-up-edge formation is a common problem in the machining of this alloy. A high pressure coolant supply with its cooling and lubrication ability was found to be very helpful for decreasing the coefficient of friction and temperature during the process, consequently lowering progression of wear and cutting force components when compared to other cooling and lubrication conditions tested in this study. The greatest tool life is achieved by high-pressure coolant supply, and cryogenic cooling achieves the second greatest tool life. Minimum quantity lubrication is found to be inefficient for improving the machining performance of this alloy. Finally, it is found that the selected depth of cut has vital effect on the penetration capability of cooling and lubrication in between tool and chip, and consequently, it plays a significant role in the contribution of cooling and lubrication to the machining performance of this alloy.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The partial strengthening method for pre-stamped panels both avoids excessive strength enhancement over the entire product and substantially reduces the processing cost compared to conventional hot press forming. In this paper, we propose two types of partial strengthening processes to selectively increase the local strength of a cold stamped B-pillar by utilizing an induction coil system and water spray quenching to induce the martensitic transformation in the target region. Thermo-mechanical FE analyses were conducted to evaluate the effect of the process parameters such as the quenching rate, quenching time, and heating width on the shape changes during the partial strengthening processes while simultaneously considering the thermal dilatation and transformation plasticity.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉The monitoring of rotating machinery condition has been a critical component of the Industry 4.0 revolution in enhancing machine reliability and facilitating intelligent manufacturing. The introduction of condition-based monitoring has effectively reduced the catastrophic events and maintenance cost across various industries. One of the major challenges of the diagnosis remains as majority of the diagnostic model requires off-line analysis and human intervention. The offline analysis, which is normally done by previous experience, involves tuning model parameters to improve the performance of the diagnostic model. However, for newly developed models, the knowledge of the unknown parameters does not exist. One way to resolve this issue is through learning using adaptation. The adaptation algorithm adjusts itself by newly acquired data. Hence, improvement of the model performance is achieved. In this paper, a nonlinear adaptive dictionary learning algorithm is proposed to achieve early fault detection of bearing elements without using the conventional computation heavy algorithm to update the dictionary. Deterministic and random data separation is implemented using the autoregressive model to reduce the background noise. The filtered data is further analyzed by the Infogram to reveal the impulsiveness and cyclostationary signature of the vibration signal. The dictionary is initialized using random parameters. Instead of using the 〈em〉k〈/em〉 means singular value decomposition algorithm to compute the dictionary for adaptation, the unscented Kalman filter (UKF) is implemented to update the dictionaries using the filtered signal from the Infogram. The updating algorithm does not require computation of the dictionary, and no previous knowledge of the dictionary’s parameters is needed. The updated dictionary contains the detected fault signature from the Infogram and, therefore, is used for further fault analysis. The proposed algorithm has the advantage of self-adaptation, the capability to map the non-linear relationship of the signal and dictionary weights. The algorithm can be used in the various condition-based monitoring of rotating machineries to avoid additional human efforts and improve the performance of the diagnostic model.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉This work investigates the surface modification of quenched and tempered AISI H13 tool steel, widely used in mold-making industry, by sinking EDM with very fine Si powder suspended in the dielectric. The output variable resultant friction coefficients, wear resistance, and hardness of recast layer were measured for different input variables. The 1 A/2.8 μs and 2 A/3.2 μs and 2 A/6.4 μs combinations of discharge current and discharge duration, respectively, produced high hardness, low friction coefficient, and high wear-resistant recast layers, after the formation of martensitic phases in the recast layer as well as C0.17, Fe0.81, Si0.02 carbide. Layer thickness tends to grow with machining time. PMEDM process produced variable amounts of Si in the resultant recast layers, forming iron-silicon carbide phases. Lower wear rates were measured for the high-quality recast layers tested favoring the lifetime of this tool steel in abrasive applications. Martensitic phase formation in the recast layers helps explaining the increased hardness.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉In ultra-precision turning of large optical components, the surface quality deterioration caused by tool wear has severely restricted the optical performance of these components. To investigate the effects of tool wear on surface micro-topography, this paper conducts an experimental study on the ultra-precision turning of copper. The wear characteristics of the diamond tool and the micro-topography of the ultra-precision turned surface at different cutting distances are discussed and evaluated. The plastic deformation behavior of the workpiece material is investigated at various cutting parameters and tool wear conditions. Furthermore, the power spectral density (PSD) and the diffraction optical characteristics of the machined surface are achieved and analyzed quantitatively. The experimental results show that during diamond turning of copper, the tool wear is mainly characterized by the micro-breakages on the tool edge when the cutting distance is less than 24 km. With the increase of the cutting distance, the micro-breakages gradually develop into the continuous wear land, and the enlarged wear area is attributed to the cumulative cleavage fractures and uniform mechanical wear. Moreover, the increased tool wear can result in more pronounced periodic surface micro-topography and greater height of the material pile up, which will deteriorate the optical performance and enhance the diffraction effect of the ultra-precision turned surface.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉In this research, the effect of stress relief annealing heat treatment on mechanical properties, microstructure, and residual stresses of a severe plastic deformation technique, known as constrained groove pressing (CGP), was investigated. For this purpose, the CGP process was performed on the commercial pure copper sheet with 3-mm thickness. The hardness, strength, homogeneity, microstructure, and residual stresses before and after stress relief annealing heat treatment were evaluated. Hardness and homogeneity on the surface and thickness were investigated and strength in both of groove direction and transverse groove direction were determined. Also, microstructure was studied along the thickness of CGPed samples, and the contour method was used for 2D residual stress measurement. The results indicate, with increasing number of CGP passes, hardness, strength, and homogeneity increase, while the mean grain size and residual stress decrease. Stress relief annealing reduces the mean grain size in the first pass but increases the mean grain size in the subsequent passes, causing a decrease of mechanical properties. Also, stress relief annealing increases residual stresses due to increasing microstructure heterogeneity.〈/p〉

Beschreibung: 〈p〉The original version of this article contained a mistake. Due to technical problems at the typesetter, author corrections were not carried out correctly. The original article has been corrected.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Agile joint jig (AJJ) is a novel and promising reconfigurable assembly jig, which is put forward to deal with the disadvantages of traditional dedicated assembly jig in aerospace industry. For AJJ design, it is under the combined influence of aircraft product and assembly process requirements, especially the experience and knowledge of designers. Although case-based reasoning (CBR) gives the possibility to make fixture design more efficiently, this method has its weakness that the most similar case maybe is not the optimal selection and the designers still depend on their knowledge to determine what changes need to be made and how these changes can be achieved. In order to lower the requirement for designers’ skills and enhance the AJJ design efficiency, this paper presents an intelligent configuration method based on smart composite jig model (SCJM). Firstly, the concept and definition of SCJM are presented. It is not only a generic assembly jig architecture for a certain aircraft product family but also appends information and knowledge through MBD (model-based definition). Secondly, the requirement information model including product general information and assembly process information and so on is established with MBD for driving AJJ design automatically. Based on the above models, the intelligent configuration method for AJJ is proposed and realized by combing auto-selection reasoning with auto-assembly reasoning. The auto-selection reasoning is to achieve that the standardized components are selected actively by matching attributes between SCJM and product model. The auto-assembly reasoning is to automatically assemble the selected components in terms of the typical constraint relationships. By these ways, the SCJM can perceive the product assembly requirements by itself and then achieve appropriate design automatically. Finally, a computer-aided system for intelligent design of airplane assembly jig was developed. The results indicated that the proposed methods are able to significantly improve the design efficiency and quality of reconfigurable assembly jig.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Recently, energy-efficient process planning has aroused numerous concerns from both industry and academia. However, as one of the most important tasks of process planning in discrete parts manufacturing system, tool selection has seldom been investigated in terms of energy efficiency. Without a good understanding of its effects on energy efficiency of machining process, energy-efficient manufacturing cannot be achieved to a satisfactory level. To bridge this research gap, this paper studies tool selection effects by analysing tools with different geometrical parameters, i.e. cutter radius, flute number and helix angle. Their effects on energy efficiency of slot milling process are analysed using experimental approach and theoretical approach, respectively. In experimental approach, Taguchi method is firstly applied to study the effects of each tool geometrical parameter. Then, analysis of variance (ANOVA) is performed to study the significance of each factor. In theoretical approach, the influence of tool selection on cutting power is analytically revealed. Subsequently, the energy efficiency of different cutters is quantitatively analysed through numerical experiments. The results are quite promising with both approaches leading to the same conclusion. The rank of influence is cutter radius 〉 flute number 〉 helix angle. Both methods suggest that a milling cutter with a larger cutter radius and fewer flutes will improve the energy efficiency in milling process. Although there is a small discrepancy in helix angle, it does not affect the good agreement of these two methods since the influence of the helix angle is nearly negligible. Compared to experimental approach, theoretical approach may have more application potential since it may help reduce time and waste of materials. To the best knowledge of the authors, the effects of tool selection on energy efficiency in milling process are systematically analysed for the first time, which significantly advances the state of the art in energy-efficient process planning.〈/p〉

Beschreibung: 〈p〉Author Meiping Wu wmp169@jiangnan.edu.cn should also be declared as the corresponding author of the article 〈span〉https://doi.org/10.1007/s00170-018-2549-x〈/span〉.〈/p〉

Beschreibung: 〈p〉Author Meiping Wu wmp169@jiangnan.edu.cn should also be declared as the corresponding author of the article 〈span〉https://doi.org/10.1007/s00170-017-1504-6〈/span〉.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Selective laser melting (SLM) technology is playing an increasingly important role in today’s manufacturing industry. However, the surface quality of SLM samples is relatively poor and cannot be directly applied to industrial production. Therefore, this paper focuses on the post-treatment process of SLM AlSi10Mg alloy. First, the rough machining is performed by a grinding process (GP), and then, the magnetic abrasive finishing (MAF) is used for finish machining. The experiment results show that the combination of GP and MAF can effectively reduce the surface roughness and improve the surface quality of SLM AlSi10Mg alloy. The GP reduced the surface roughness to drop from 7 μm (after SLM forming) to about 0.6 μm, and the rough surface with defects such as spheroids and pits evolved into the fine surface with scratches and pores. The MAF reduced the surface roughness to a minimum of 0.155 μm, which resulted in excellent surface morphology. The surface hardness after the GP was higher, and the MAF reduced the hardness of the GP surface.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉In this study, TiNiAl-SiC composites (TMCs) containing 1, 3, and 6 wt% SiC were prepared by spark plasma sintering (SPS) process using heating rate of 100 °C/min, at 800 °C, and sintering pressure of 40 MPa, and holding time of 10 min. Phase identification was carried out on TiNiAl-SiC composites by X-ray diffraction technique. Microstructure and elemental analyses were done with a scanning electron microscope (SEM) and energy dispersive X-ray (EDS) spectroscopy. SEM micrographs showed pronounced grain boundary interaction between the SiC and the TiNiAl matrix with increase wt% SiC. The results from the mechanical characterization generally showed enhancement in hardness, tensile strength, yield strength, and wear. At 6 wt% SiC, the optimum values of 2852 MPa, 930.46 MPa, and 673.02 MPa were established for hardness, tensile strength, and yield strength, respectively. Also, TiNiAl-SiC composite with 6 wt% SiC presented the best frictional profile with the highest resisting power due to the lowest friction coefficient of about 0.4, and the wear rate of 2.18 mm〈sup〉3〈/sup〉/m. The absence of grooves in the worn morphology also confirmed that it has good tribological properties.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Commercially available grades of poly(lactic acid) (PLA) and acrylonitrile-butadiene-styrene (ABS) were printed in different shapes using an additive manufacturing (AM) printer based on material extrusion (ME). It is known that the quality of a 3D printed sample is closely connected to the rheological properties of the polymer matrix. However, some printing parameters, such as the feed rate and the print speed, might not be determined only by equipment design as usually reported in the literature. Instead, the thermal and rheological properties of the polymers should be carefully considered. The focus of many studies has relied on optimizing the specific properties of an ME printer through the adjustment of the printing parameters. Still, few researchers have shown how the rheological behaviour of a material can affect its final properties. Therefore, this paper would like to answer satisfactorily some recurring questions with clear practical importance, which is related to the fact that some materials have better print quality than others do and about the feasible margins for increasing the print speed according to the characteristics of a polymeric material. Thus, in this work, rheological characterization of the resins was conducted and it was detected that the processing condition for a specific thermoplastic is highly dependent on its rheological behaviour. A method of mass flow conservation was presented for determination and consideration of the rheological characteristics when selecting an appropriate process parameter for the additive manufacturing system. It was found that even a small recovery strain resulting from the characteristic morphology of ABS could provide lower layers’ roughness and good printing quality to the 3D printed samples. Thus, the main goal of this work was to evaluate the importance of the rheological properties of common thermoplastics used in extrusion-based process on the controlling of a 3D printer and on the final printing quality.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Industrial waterjet stripping/cleaning is a prime example of a dull, dirty, dangerous manufacturing process that is ripe for automation, yet it remains a manual task in most instances due to complex workpiece geometry and/or low-volume, high-mix production. Recently developed automated tool trajectory planning algorithms and collaborative path planning frameworks offer a potential solution but are of limited use without corresponding process models and simulation tools to evaluate toolpath quality. Existing process models do not consider the spray impingement angle or the cumulative effect of successive tool passes—both of which are inevitable when spraying geometries that possess concave and/or discontinuous features. This research proposes a novel process model that includes impingement angle and accounts for the cumulative, ablative nature of the process. It also develops a simulation algorithm that applies this model to complex geometries while considering shading effects caused by protrusions and overhangs. Model parameters are determined via a design of experiments approach and nonlinear regression, and verification experiments on complex test parts show good agreement between predicted and measured results. Paired with the aforementioned trajectory planning tools, this research represents a complete robotic process planning solution for waterjet stripping/cleaning of complex parts in high-mix, low-volume manufacturing.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉γ-TiAl alloy is an advanced material with a vast prospect of applications, but its processing is a well-known engineering problem. In this article, the optimum range of cutting parameters of cemented carbide tool has been obtained by several turning experiments. In fact, tool wear has a great effect on cutting force. These four major effects, flank wear width, cutting speed, cutting depth, and feed rate on turning force, have been carefully discussed. Meanwhile, the turning force model of γ-TiAl alloy has been established. This model studied both the cutting force on rake face and the wear effect force on flank face. Several key coefficients have been determined by fitting the extensive experimental results. Later, the accuracy has been examined. The experimental results show tool life is short and tool wear is intense in general. At the cutting speed of 50 m/min, when feed rate does not exceed 0.1 mm and cutting depth does not exceed 0.3 mm, tool life is relatively longer and surface quality is relatively better. Within this range, the cutting force is approximately linear with respect to the cutting depth and the feed rate. In addition, the cutting force will increase significantly with the increase of the flank wear width. It turns out the model has a higher accuracy and it can appropriately reflect the change of cutting force.〈/p〉

Beschreibung: 〈h3〉Abstract〈/h3〉 〈p〉Application of external magnetic field in electrical discharge machining is one of the methods to increase this process capability and decrease its limitations. In the present study, a single discharge in magnetic field-assisted electrical discharge machining has simulated using finite element method in order to obtain the temperature distribution and generated crater dimensions on the workpiece surface. A new mathematical model for plasma channel radius was also developed and used at simulation stage. Regarding good agreement between recast layer thickness obtained by numerical and experimental methods with maximum error of 8.8%, the effects of applying external magnetic fields on plasma flushing efficiency and recast layer thickness were found numerically and experimentally. Also the influences of pulse current and pulse on-time on dimensions of generated craters at magnetic field-assisted EDM were studied numerically. The results showed the positive effects of application of external magnetic field in EDM process on increasing plasma flushing efficiency and decreasing recast layer thickness.〈/p〉